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Decreasing TE-LSP bandwidth, "interoperability issue" (fwd)

  • From: "Thomas D. Nadeau" <tnadeau@cisco.com>
  • Date: Wed, 06 Nov 2002 17:08:12 -0500
  • Cc: Shahram Davari <Shahram_Davari@pmc-sierra.com>, "'George Swallow'" <swallow@cisco.com>, David Allan <dallan@nortelnetworks.com>, Der-Hwa Gan <dhg@juniper.net>, "Gray, Eric" <egray@celoxnetworks.com>, mpls@UU.NET, swallow@cisco.com


         Since George beat me to the punch, I will just
add a few points to his.

>Shahram -
>
> > The LSP-ID defined in Y.1711 is essentially a combination of LSP-ID + 
> Tunnel-ID
> > as defined in RSVP-TE.
> >
> > In the current version of Y.1711, 4 bytes are assigned to
> > this. However the current version of Y.1711 sets the first 2 octets of
> > this field to zero for future use. Therefore two methods are possible:
> >
> > 1) Compress the LSP-ID + Tunnel-ID in to 2 bytes
>
>This uses up all the space.  If RSVP-TE is the only application for
>Y.1711 then this would be acceptable.  But since it's called MPLS OAM,
>I assume there were other apps in mind as well.

         Yes, for example, what do we do for L2/L3 VPN given
this logic?

> > 2) You could use the first 2 octets, and encode the 2-byte RSVP-TE
> > LSP-ID in the first 2 octets of Y.1711 LSP-ID and encode the 2-byte
> > RSVP-TE Tunnel-ID in the last 2 octets of Y.1711 LSP-ID.
>
>Not enough space to be future proof.  We already have requests to
>support thousands of tunnels.  If I give just 4 bits to LSP-ID that
>only leaves 4k tunnels.

         There are several deployments with tens-of-thousands
of tunnels, so this will definitely not work there.

         --Tom


> > Just a question, isn't it possible to change the LSP by changing the
> > Tunnel-ID, rather than LSP-ID?
>
>You cannot share bandwidth between different RSVP sessions only
>between different senders.  The tunnel ID is in the session ID to say
>"the various LSPs with this identification all belong to the same
>tunnel".
>
>The LSP-ID is in the sender template so that they can be
>distingueshed, yet associated via the session and thus can share
>bandwidth.
>
>...George
>
>==================================================================
>George Swallow       Cisco Systems                  (978) 497-8143
>                      250 Apollo Drive
>                      Chelmsford, Ma 01824

Success is relative; the more success, the more relatives. -Anonymous